Effects of droplet diameter on instantaneous burning rate of isolated fuel droplets in argon-rich or carbon dioxide-rich ambiences under microgravity

2013 ◽  
Vol 34 (1) ◽  
pp. 1601-1608 ◽  
Author(s):  
Shinji Nakaya ◽  
Kotaro Fujishima ◽  
Mitsuhiro Tsue ◽  
Michikata Kono ◽  
Daisuke Segawa
Keyword(s):  
Carbon Dioxide ◽  
Burning Rate ◽  
Droplet Diameter ◽  
Fuel Droplets

The Combustion Characteristics of n-Decane/Iso-Octane/Toluene Mixture and Jet-A Fuel Droplets in the Absence of Convection

2011 ◽  
Author(s):  
Yu-Cheng Liu ◽  
Anthony J. Savas ◽  
C. Thomas Avedisian
Keyword(s):  
Burning Rate ◽  
Droplet Diameter ◽  
Mixture Fraction ◽  
Combustion Characteristics ◽  
Aviation Fuel ◽  
Ternary Blend ◽  
Transportation Fuel ◽  
Spherical Droplet ◽  
Burning Process ◽  
Fuel Droplets

This study examines the extent to which a ternary mixture of n-decane/iso-octane/toluene in the specific mixture fraction of 42.67/33.02/24.31 (mole fraction), respectively, can replicate the droplet burning characteristics of an aviation fuel, Jet-A (designated by the Air Force as “POSF4658”). Experiments were carried out to examine the droplet combustion characteristics in an environment which minimizes convection to promote spherical symmetry in the burning process. The evolution of droplet diameter, burning rate and flame and soot stand-off ratios were compared to Jet-A to evaluate the potential of this ternary to serve as a Jet-A surrogate regarding the droplet burning process. The results show that the ternary blend has a shorter transient droplet heating period than Jet-A and it closely replicates the evolution of droplet diameter and burning rate. The burning rates for these two fuels are close at the end of burning, and flame and soot standoff ratios for the ternary are also reasonably close to those of Jet-A. The results also suggest that the spherical droplet flame configuration can be a useful tool to evaluate the extent to which a mixture of single component fuels may serve as a surrogate of a real transportation fuel.

scholarly journals Interactive Effects in Two-Droplets Combustion of RP-3 Kerosene under Sub-Atmospheric Pressure

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1229
Author(s):  
Hongtao Zhang ◽  
Zhihua Wang ◽  
Yong He ◽  
Jie Huang ◽  
Kefa Cen
Keyword(s):  
Burning Rate ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Ambient Pressure ◽  
Interactive Effects ◽  
Propagation Time ◽  
High Speed Camera ◽  
Single Droplet ◽  
Fuel Droplets ◽  
Spacing Distance

To improve our understanding of the interactive effects in combustion of binary multicomponent fuel droplets at sub-atmospheric pressure, combustion experiments were conducted on two fibre-supported RP-3 kerosene droplets at pressures from 0.2 to 1.0 bar. The burning life of the interactive droplets was recorded by a high-speed camera and a mirrorless camera. The results showed that the flame propagation time from burning droplet to unburned droplet was proportional to the normalised spacing distance between droplets and the ambient pressure. Meanwhile, the maximum normalised spacing distance from which the left droplet can be ignited has been investigated under different ambient pressure. The burning rate was evaluated and found to have the same trend as the single droplet combustion, which decreased with the reduction in the pressure. For every experiment, the interactive coefficient was less than one owing to the oxygen competition, except for the experiment at L/D0 = 2.5 and P = 1.0 bar. During the interactive combustion, puffing and microexplosion were found to have a significant impact on secondary atomization, ignition and extinction.

Spray and Emission Characteristics Near Lean Blow Out in a Counter-Swirl Stabilized Gas Turbine Combustor

2006 ◽  
Author(s):  
Jonathan A. Colby ◽  
Suresh Menon ◽  
Jechiel Jagoda
Keyword(s):  
Droplet Diameter ◽  
Reacting Flow ◽  
Gas Turbine Combustor ◽  
Complete Combustion ◽  
Fuel Droplets ◽  
Phase Velocities ◽  
Fuel Jet ◽  
Key Factor ◽  
Flow Features ◽  
Initial Droplet Size

An experimental study of a single, swirl cup burner is carried out to improve understanding of the lean reacting flow field near idle conditions for an annular spray combustor. The counter-swirler is mounted horizontally in a trapezoidal cross-section combustor with quartz plate walls. Liquid fuel, Jet-A, is initially atomized using a simplex nozzle, and then a designed re-atomization occurs from the swirler hardware. Measurements of non-reacting and reacting gas phase velocities enable the direct comparison of critical flow features at various power settings. Droplet diameter and exhaust composition measurements confirm that the initial droplet size is a key factor in emission levels. Smaller droplets in the spray periphery tend to evaporate and burn premixed, while larger droplets in the spray core convect downstream and burn with a sheath-type, non-premixed flame. The presence of small fuel droplets in the spray may ensure more complete combustion and improve combustor stability at lean, low power settings.

The effect of initial diameter in spherically symmetric droplet combustion of sooting fuels

1994 ◽  
Vol 446 (1927) ◽  
pp. 255-276 ◽  
Keyword(s):  
Burning Rate ◽  
Rate Constants ◽  
Soot Formation ◽  
Droplet Diameter ◽  
Droplet Surface ◽  
Spherically Symmetric ◽  
Low Gravity ◽  
Initial Droplet ◽  
Initial Diameter ◽  
Burning Rates

The effect of initial droplet diameter on the burning rate of sooting fuels – n-heptane and 1-chloro-octane – was examined experimentally at low gravity. A 1.2s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fibre-supported droplets were burned, and both techniques gave matching results for droplets of similar initial diameter. Burning rate constants for both fuels were measured for a large number of droplets ranging from 0.4 to 1.1 mm in initial diameter. Results showed that burning rate constants decreased monotonically as the initial droplet diameter was increased above 0.6 mm for both fuels. This decrease was considered to be due to the observed increase in soot formation and accumulation in a shell-like structure inside the flame of the larger droplets. The increased collection of soot inside the larger droplet flames reduced the proportional heat release from the flame and may have acted as a barrier to heat transfer from the flame to the droplet. Flame-to-droplet diameter ratio increased monotonically with time, thus suggesting that quasi-steady combustion was not achieved. The flames and soot shells for 1-chloro-octane droplets with their lower burning rates remained closer to the droplet surface than similarly sized n-heptane droplets.

Effects of Initial Diameter on Burning of Nonane Droplets in a Non-Buoyant and Buoyant Ambience: Burning Rate, Soot Formation and Flame Structure

2001 ◽  
Author(s):  
J. H. Bae ◽  
C. T. Avedisian
Keyword(s):  
Burning Rate ◽  
Droplet Size ◽  
Soot Formation ◽  
Droplet Diameter ◽  
Flame Structure ◽  
Large Droplet ◽  
Droplet Combustion ◽  
Small Droplet ◽  
Burning Process ◽  
Initial Droplet

Abstract The results from nonane droplet combustion experiments conducted at 1g and μg are analyzed and compared in the following aspects: the burning rate, soot formation, flame structure. By varying the initial droplet diameter, we observe and discuss the effect of Do on droplet burning. The μg experiments were performed in a drop tower and a drag shield was used to create a low buoyant environment All experiments were fiber-supported and used the same experimental instruments. The droplet size between 0.40 to 0.95mm was examined in the experiments. Results showed that droplet burning is nonlinear in both a buoyant and a non-buoyant environment for the initial droplet diameters examined. Soot formation, which is influenced by Do may strongly affect the droplet burning process in both environments. The large droplet produces more soot and bums slowly whereas the small droplet bums fast because there is less soot.

Combustion of a Fuel Droplet Surrounded by Oxidizer Droplets

1991 ◽  
Vol 113 (4) ◽  
pp. 959-965 ◽  
Author(s):  
Tsung Leo Jiang ◽  
Huei-Huang Chiu
Keyword(s):  
Burning Rate ◽  
Droplet Size ◽  
Size Ratio ◽  
Group Effect ◽  
Fuel Droplet ◽  
Method Of Images ◽  
Fuel Droplets ◽  
Combustion Modes ◽  
Nonspherical Shape ◽  
Positive Effect

The interaction between a burning fuel droplet and satellite oxidizer droplets is studied analytically. The effects of droplet spacing and droplet size ratio on the flame configuration of a burning fuel droplet with a satellite oxidizer droplet are analyzed in a high-temperature oxidizing environment by using the bispherical coordinate system. Three combustion modes including normal combustion, conjugate combustion, and composite combustion are identified at appropriate droplet size ratio and droplet spacing. The burning rate of the fuel droplet is found to be greater than that of an isolated burning fuel droplet, and to increase with the decreasing distance between two droplets. This result has shown a positive effect on the interaction between fuel and oxidizer droplets, in contrast to that of two interacting fuel droplets where the burning rate decreases with decreasing droplet spacing. The combustion configuration of a fuel droplet surrounded by six satellite oxidizer droplets symmetrically is also examined by the method of images. The flame that encloses the fuel droplet is found to be “compressed” and distorted to a nonspherical shape due not only to the group effect among oxidizer droplets but also to the interaction of bipropellant droplets. The results indicate that the burning rate of a fuel droplet increases and the flame size decreases significantly as a result of an increased supply of oxidizer vapor provided by the surrounding oxidizer droplets. Therefore properly optimized bipropellant combustion is potentially able to achieve a desired combustion performance with a much smaller combustor than a conventional spray burner.

Development of Fuel Droplet Vaporization Rate Measurement Techniques for Realistic Burning Spray Applications

2013 ◽  
Author(s):  
Sarah A. Tedder ◽  
Dennis J. L. Siedlak ◽  
Steven G. Carter ◽  
Daniel S. ReMine
Keyword(s):  
Stimulated Raman Scattering ◽  
Droplet Diameter ◽  
Measurement Techniques ◽  
Jet Fuel ◽  
Vaporization Rate ◽  
Rate Measurement ◽  
Support Design ◽  
Fuel Injectors ◽  
Fuel Droplets ◽  
Reduce Emissions

Technology to support design for the next generation of aircraft fuel injectors is being developed by NASA’s Fundamental Aeronautics Program to reduce emissions, increase efficiency, and enable fuel flexible aircraft. The design of these fuel injectors can be aided by measuring the vaporization rates of jet fuel droplets in realistic, burning sprays. Currently, in this environment, no instantaneous vaporization rate measurement techniques have been applied. After surveying techniques for potential development for this application, two techniques were identified: stimulated Raman scattering (SRS) and droplet lasing spectroscopy (DLS). Plans were developed for the modification of these techniques for this specific application. Developments of the SRS technique were tested including measurement of a water droplet diameter change rate. SRS spectra were also collected from jet fuel droplets.

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